The NIH/NCRR Research Resource for Complex Physiologic Signals was established in September, 1999, in order to accelerate research progress and to stimulate new basic and clinical studies of biomedical signals. This competitive renewal request proposes to enhance and expand the components of this multidisciplinary Resource, including: PhysioBank - a large and growing archive of well-characterized digital recordings of physiologic signals and related data currently includes over 35 databases of cardiopulmonary, neural and other biomedical signals from healthy subjects and from patients with a variety of conditions with major public health implications, including sudden cardiac death, congestive heart failure, Parkinson's disease, sleep apnea, and aging. Core and collaborative research supporting this component develops new databases and specialized software to assist in this process. PhysioToolkit - a large and growing library of open source software for physiologic signal processing and analysis, detection of physiologically significant events using both classical techniques and novel methods based on statistical physics and nonlinear dynamics, interactive display and characterization of signals, creation of new databases, simulation of physiologic and other signals, evaluation and comparison of analysis methods, and analysis of complex processes. A unifying theme of research projects that contribute software to PhysioToolkit is the extraction of hidden information from biomedical signals, information that may have diagnostic or prognostic value in medicine, or explanatory or predictive power in basic research. PhysioNet - the Resource's web site (www.physionet.org) provides free access to PhysioBank and PhysioToolkit, and facilities for discussion and cooperative analysis of data and algorithms. PhysioNet offers a growing set of tutorials to assist in training investigators, clinicians and students in complex signal analysis. PhysioNet also hosts a highly successful series of open challenges that focus research efforts and promote rapid progress on important basic and clinical research questions. We also propose to develop new data analysis and archival biotechnology tools in support of the missions of the NCRR's General Clinical Research Centers, and to expand our core and collaborative research directed at a wide range of basic and clinical problems, including infant apnea, Parkinson's disease, and life-threatening cardiac arrhythmias.